James Jones is the API Guru of the Canvas Community, and among his many "Canvancements," the one I depend on most is his script to Adjust All Assignment Dates. I use a microassignments approach in my classes, where students choose from about a dozen assignments every week, so I have over 200 items in my Gradebook. Using James's script, I can see all my assignment dates (due dates and available-until dates) in a Google Sheet and adjust the dates there. Plus I can also change the names of assignments too, changing as needed and making sure I'm consistent.
When you copy a course in Canvas, it offers a single date adjustment but that doesn't work for me: in the Fall semester the Thanksgiving Break comes at a different time during the semester than Spring Break, which throws my dates off. With James's spreadsheet-based approach, that's easy to manage!
And now, in the midst of Spring 2020, if you need to be changing dates in an existing course, this tool might make it easier for you, depending on how many dates you need to change. For me, this tool is so much faster and also more reliable than making manual adjustments!
James provides details instructions on the Adjust All Assignment Dates page, and he has created several videos to help you do that! Here's a playlist of the videos:
Since I love using Google Sheets and formulas in Google sheets, this approach to managing dates/times works great for me!
Here's a screenshot of what that looks like; so useful! You will probably find other useful scripts in the complete list of James's Canvancements.
